977 Development of a Non-Small Cell Lung Cancer PDX Model in a Myeloid-Boosted Humanized Host Highlights a M2 Polarization Phenotype Within the Myeloid Compartment

Background Despite immunotherapy advanced the way Non-Small Cell Lung Cancer (NSCLC) patients are treated in the clinic, patients outcome is still unpredictable.1 The tumor microenvironment (TME) plays a central role in early establishment, progression, and metastasis in NSCLC. Specifically intrinsic TME factors can lead to inflammatory or immune-suppressive phenotypes. Innate immunity and particularly the macrophage population influences TME behavior. Macrophages in non-responsive patients are polarized towards the M2-type, which are known to dampen the immune response by secreting anti-inflammatory factors including IL-10 and TGF-β.2 Given the central role of macrophages in modulating the TME in NSCLC patients, it becomes important to leverage model systems in which macrophage’s phenotype recapitulates the TME composition of NSCLC patients. Syngeneic models are characterized by their murine immune system which is very different from the human system. Thus, these models are not ideal to study the human immune response to various therapeutics nor to study the human cellular interaction within the TME. Intrinsic tumor heterogeneity is one of the main factors driving tumor progression and response. For this reason, immortalized cell lines are not an ideal system to represent the diversity of the patient population.3 Methods In order to dissect the mechanism underlying immunosuppression in cancer, we need to combine two clinically relevant platforms: a patient-derived xenograft (PDX) model which represents the necessary human tumor heterogeneity; a humanized model which reliably recapitulates the complexity and functionality of the human myeloid compartment. These two requirements within the same model overcome species specific limitations and compensate for tumor heterogeneity. Champions Oncology partnered with TranCure BioServices to generate a NSCLC PDX model implanted in a host reconstituted with human functional immune system. This platform is enhancing human myeloid cell engraftment through a physiological boost of human cytokines. Results Flow cytometry analyses showed that CD34+Human Stem Cell (HSC) engraftment was stable up to 3 months, as a result of hydrodynamic boosting. Monocytes and various dendritic cell populations were detected in the blood and bone marrow, while permitting functional lymphocyte establishment. Deeper characterization of the model exhibited a skewed M2 phenotype within the macrophage population, providing evidence of the immunosuppression properties in this NSCLC model. Conclusions Overall, our studies lead to the generation of a fully humanized model retaining the heterogeneity of the patient’s NSCLC disease, which enables researchers to confidently study immune suppression and macrophage polarization. This platform is ideal to evaluate a therapeutics’ ability to modulate immunosuppression-boosting immunotherapy response. References Mamdani H, Matosevic S, Khalid AB, Durm G, Jalal SI. Immunotherapy in Lung Cancer: Current Landscape and Future Directions. Front Immunol 2022;13. Mantovani A, Allavena P, Marchesi F, Garlanda C. Macrophages as tools and targets in cancer therapy. Nat Rev Drug Discov 2022;21:799–820. Proietto M, et al. Tumor heterogeneity: preclinical models, emerging technologies, and future applications. Front Oncol 2023;13:1164535. Ethics Approval All human biological samples utilized for the research described in this abstract have been procured or collected after an Informed Consent form has been issued according to the current local legislation. All animals studies described in this abstract have been conducted under Champions’ and TransCure BioServices’ approved IACUCs.